1. Field of the Invention
This invention relates to an apparatus and process for restricting fluid flow in a pipe. More particularly, this invention relates to an apparatus and process for rapidly controlling fluid flow in a pipeline in cases of leaks or the necessity for repairs or maintenance. The apparatus and process of this invention relates in one embodiment particularly to an improved sleeve for insertion, through a side wall hole of substantially less diameter than the diameter of the pipeline, into a pipeline where it is inflated thereby restricting flow of fluid within the pipeline and a method of its insertion into the pipeline.
Flow control valves frequently are available along a pipeline and closing of the valves for isolation of a damaged section of a pipeline will reduce the loss of fluid. However, such valves in most pipelines are spaced far apart, frequently many miles apart, rendering effective restriction of the pipeline under emergency conditions impractical through use of such valves and of inconvenience to all customers being served by that section of pipeline. Even when the flow control valves are closed and a ruptured section of pipeline isolated, the static pressure within the pipeline will cause the fluid to flow out of the rupture resulting in loss of a large amount of fluid. Thus, it is highly desirable that the flow of fluid inside the pipeline be stopped or restricted across a short distance at the point of damage or rupture. Frequently the maintenance of a pipeline requires temporary restriction of fluid flow within the pipeline. If flow control valves are not present at desired locations, pinching of the pipeline with mechanical or hydraulic tools to halt the flow has been practiced. However, such operation can weaken the pipe or require the pinched section to be replaced subsequent to the other maintenance. The installation of temporary valves near the rupture site or the maintenance site is practiced. In both gas and water distribution systems, there is a need to have an easy and versatile device and method to halt the flow of fluid within a short distance of a break or maintenance point.
2. Description of the Prior Art
A wide variety of devices and methods have been used to stop fluid flow in pipelines. One group of methods that has been used for stopping low pressure flow involves the direct injection of material such as viscous grease and expandable foams. Such methods are applicable only to pipelines operating at pressures in the order of 1 psi and less and has the serious disadvantage of necessity of removal of the injected material to reopen the pipeline.
Another method currently used by the gas distribution industry, involves the insertion of a rubber bag through the pipe side wall upstream from a leak or desired work point and subsequent inflation of the bag with compressed gas to effect a seal inside the pipe. Such rubber bags may be sperical in shape such as the "Gardner-Goodman Stopper" as sold by Safety Gas Main Stopper Co., Inc., Brooklyn, N.Y., or they may be cylindrical shaped such as the "Goodman Cylindrical Stopper" as sold by Safety Gas Main Stopper Co., Inc. However, the inflatable bags only are useful under low pipeline pressures, generally under 5 to 10 psi and considerably less with large diameter pipes. Attempts have been made to increase operability of inflatable stopping devices under higher pressures by insertion through a separate hole of a device having multiple blades which mechanically open to cover a substantial portion of the cross-sectional area of the pipeline. When used in conjunction with inflated bags, such a device uprates the pressure at which the stopping device may be used to a maximum of about 30 psig, as compared with the inflatable bag alone. Such devices which are suitable for insertion through side wall fittings are more fully described in the article, "An Improved Flow-Stopping System for Distribution Main" by A. R. Caruthers and D. R. Casson, I.G.E. Journal, pp. 183-192, June 1973. Another inflatable bag-type line stopper insertable through the pipe side wall is disclosed in U.S. Pat. No. 3,842,864.
Other expandable pipe plugs of the type inserted through an open end of the pipe or through a pipe fitting, such as an elbow, a Y or a T, having an opening substantially the same diameter as the pipe to have its flow restricted are described in U.S. Pat. Nos. 4,144,908, 3,498,333 and 2,843,154. U.S. Pat. No. 3,870,085 describes expansible plugs for sewer pipes which plugs have rigid end discs of a diameter about 75 percent the diameter of the pipe. The pipe plugs disclosed in these patents are only suitable for insertion through an open end of the pipe or through a fitting having an opening near the size of the pipe itself and are entirely unsuited for insertion through a hole drilled in the pipe side wall which hole has a diameter substantially smaller than the diameter of the pipe itself.